Methodology to measure seat belt fit in relation to skeletal geometry using an upright open MRI

OBJECTIVE

Poor seat belt fit can result in submarining behavior and injuries to the lower extremity and abdomen. While previous studies have explored seat belt fit relative to skeletal landmarks using palpation, medical imaging remains the gold standard for visualizing and locating skeletal landmarks and soft tissues. The goal of this study was to create a method to image automotive postures and seat belt fit from the pelvis to the clavicle using an Upright Open MRI.

METHODS

The posture and belt fit of 10 volunteers (5M, 5F) were measured in an Acura TLX in each subject's preferred driving posture and a standard reclined posture, and then reproduced in a custom non-ferromagnetic seat replica in the MR scanner with an MRI-visible seat belt. The MRI sequence and coil placement were designed to yield clear visualization of bone, soft tissue borders, and the seat belt markers in separate scans of the pelvis, lumbar, thoracolumbar, and thoracic regions. A process was developed to precisely register the scans, and methods for digitizing spinal and pelvic landmarks were established to quantify belt fit.

CONCLUSIONS

This method creates opportunities to study variation in seat belt fit in different automotive postures, for occupants of different sexes, ages, BMIs, anthropometries, and for pregnant occupants.

The Lack of Sex, Age, and Anthropometric Diversity in Neck Biomechanical Data

Female, elderly, and obese individuals are at greater risk than male, young, and non-obese individuals for neck injury in otherwise equivalent automotive collisions. The development of effective safety technologies to protect all occupants requires high quality data from a range of biomechanical test subjects representative of the population at risk. Here we sought to quantify the demographic characteristics of the volunteers and post-mortem human subjects (PMHSs) used to create the available biomechanical data for the human neck during automotive impacts. A systematic literature and database search was conducted to identify kinematic data that could be used to characterize the neck response to inertial loading or direct head/body impacts. We compiled the sex, age, height, weight, and body mass index (BMI) for 999 volunteers and 110 PMHSs exposed to 5,431 impacts extracted from 63 published studies and three databases, and then compared the distributions of these parameters to reference data drawn from the neck-injured, fatally-injured, and general populations. We found that the neck biomechanical data were biased toward males, the volunteer data were younger, and the PMHS data were older than the reference populations. Other smaller biases were also noted, particularly within female distributions, in the height, weight, and BMI distributions relative to the neck-injured populations. It is vital to increase the diversity of volunteer and cadaveric test subjects in future studies in order to fill the gaps in the current neck biomechanical data. This increased diversity will provide critical data to address existing inequities in automotive and other safety technologies.

The utility of tracheal aspirate cultures in the immediate neonatal period

OBJECTIVE

Determine the contemporary incidence of pathogenic tracheal aspirate (TA) cultures when obtained within 12 h of birth, and to associate TA culture results with specific clinical conditions that increase the risk of infection.

STUDY DESIGN

A retrospective study over a 6-month period of admissions to a single outborn neonatal intensive care unit when a TA sample was collected within 12 h of birth (n=139).

RESULT

In total, 9 of 139 (6.5%) TA cultures were positive for pathogenic bacterial growth. Maternal fever (relative risk (RR)=7.7, P<0.04) and clinical chorioamnionitis (RR=6.4, P<0.02) were significantly associated with pathogenic TA culture results. Infants with a pathogenic TA culture had lower white blood cell counts (7,500 vs 13,900 mm(-3), P<0.05) when compared with infants with a negative culture. In eight of the nine patients with pathogenic cultures, either the mother or the infant received antibiotics before TA sample collection.

CONCLUSION

Early TA culture is a helpful tool in diagnosing pneumonia, especially in certain clinical scenarios, including maternal fever, clinical chorioamnionitis and leukopenia. Administration of antibiotics before sample collection does not seem to preclude culture growth.

Unsuspected transection of lung by pigtail catheter in a premature infant

Thoracostomy tubes are commonly required to treat pnuemothoraces in premature infants. Evidence of impalement of the lungs by tube thoracostomy has been seen in autopsy studies. In neonates, there has been described a surprisingly high incidence of lung perforation. The premature lung is thought to be at greater risk for this complication owing to the pliant, thin chest wall, the proximity of vital tissues and the fragility of the lung tissue itself. The modified Fuhrman catheter, or polyurethane pigtail catheter, has been developed for the drainage of pneumothorax in premature infants. In a study of complications of the placement of pigtail catheters, no instance of penetration of the lungs was reported. We report the case of a premature infant with pigtail catheter placement that, at autopsy, was found to have impaled the lung and discuss the incidence of lung injury associated with invasive management of pnuemothoraces.